Influential U.S. Senator John McCain (Republican-Arizona) says peace in Afghanistan or elsewhere in the region is not possible without the involvement of Pakistan.

McCain, a former U.S. presidential candidate, said on July 2 during a visit to Islamabad that "we will not have peace in the region without Pakistan."

The comments come after Reuters news agency quoted two U.S. officials last month as saying the administration was considering hardening its attitude toward Islamabad because of the ease with which Pakistan-based militants have been able to launch attacks across the border in Afghanistan.

"Our relationship is more important perhaps than ever before," McCain said as he left a meeting with Sartaj Aziz, Pakistan's top foreign-policy official, and army chief General Qamar Javed Bajwa.

Aziz said that the strategic partnership between Pakistan and the United States was "critical to achieve peace and stability in the region and beyond."

McCain was accompanied by a bipartisan group of senators -- Lindsey Graham, Elizabeth Warren, Sheldon Whitehouse, and David Perdue.

U.S. critics say Islamabad is not doing enough to crack down on extremist networks. They claim that militant safe havens in Pakistan have allowed Taliban-linked extremists to plan attacks in Afghanistan and to return to safety.

Pakistan says it has helped track down terrorists, suffering hundreds of deaths itself in Islamist militant attacks in response to the crackdowns.